→ ring a bell
Linking to the video so people know what you (and I) are talking about:
In which I will have to agree with the majority of what Kenshin said above and this video kind of shows. Especially the part with Leavanny in which it easily dodges a Close Combat (that wouldn't be very effective on the Bug/Grass Pokemon anyways). Also it looks like Pignite might have taken Hydreigon down but lost to Samurott. Or somehow took Samurott down and lost to Hydreigon? The former seems more likely but I'm bad at predicting these kinds of things. Though they didn't show any part of what could be a battle between Virgil and Ash so that is something that still needs to be found out at all.
As for N .... it looks like that the idea of Plasma stopping the league or halting it might actually become reality (which is what I personally wanted but said it was unrealistic ... it kind of became more realistic). That or Ash loses and then we jump to Plasma but then I would think they would have done the preview a bit differently.
As for Eevee the only way Eevee can possibly evolve mid-battle (unless they show us a new way to evolve with it) is if it learns a new move during the battle. Someone speculated gender-related but I'm not quite sure how that could be pulled off.